Electroplating bath



Fatented daily 3,, ligfi r -icn anscrnoranrmo earn William S. Murray, liltica, and Daniel Gray, Sherrilll, N. :Y., assignors to @nsida @omrnunity, Limited, Oneida, N. it... a corporation of New York No Drawing. Application April 26, 1932, Serial No. 607,660

12 Claims.

period of time, for example, considerably more than forty-eight hours, and also so that the bath will retain its stability when heated, whereby precipitation of the indium with time or elevated temperatures is greatly retarded or eliminated.

A bath for electrodepositing indium may be made up as follows:

Free potassium cyanide 7V ozs. per gal. Indium in the form of notessium-indium cyanide 5 ozs. per gal.

The bath may be used at a temperature of about 20 0., with a current density of about 0.25 amperes on 15 square inches of surface, although it will be understood that the bath may be used at varying temperatures and with different current densities.

In accordance with the present invention a bath similar to or such as the foregoing is stabilized by the addition of a suitable saccharide, such for example, as glucose, dextrose, fructose, lavulose,

, saccharose, lactose or maltose.

The stabilizing substance may be added to the bath in an amount equal to half the quantity of the potassium-indium cyanide, although it will be understood that different amounts of the stabilizer may be added.

By way of example, however, where the hereinabove mentioned bath formula is employed, 2 /2 ozs. of dextrose per gallon may be used. It will be understood also that either potassium or sodium cyanide may b used in the bath.

The bath may be made up by first preparing a very concentrated solution of the selected cyanide. To the cyanide solution may be added about half as much dextrose by weight as the weight of indium to be added.

The indium may be addedvin several ways. For example, a solution of indium chloride, -sulphate or -nitrate, or other soluble indium salts may be poured directly into the concentrated cyanide solution; or the indium may be precipitated as fe'rro-cyanide, using sodium ferro-cyanide added to an'acid solution of indium. The use of ferrocyanide has the advantage that it may be washed at leisure, dried and left for some time and still be soluble in cyanide solution.

A preferred procedure for adding the indium, however, is to precipitate indium hydroxide from an indium chloride solution, using a small excess of ammonia. This hydroxide is washed rapidly by suction and is preferably added as quickly as possible to the cyanide solution containing the stabilizer. The amount of ammonia used is important. Enough should be used to complete the precipitation, but not an excess which would cause the precipitate to be slimy and diificult to filter and wash quickly.

By the present invention a very clear and nearly colorless bath may be made, stable enough under heat to be boiled down to a considerably less volume without precipitating the indium. Such a bath may stand for days, in fact long enough to evaporate to a crystalline mass. With the addition of water the material could still be used for a plating bath.

n will be understood that the stabilizer of the present invention may be used in baths for plating with indium alloys, such for example, as-in a bath for plating with an alloy of silver and indium.

What is claimed is:

1. In the process of electrodepositing indium, the step which comprises preparing a cyanide indium plating bath and adding dextrose thereto.

2. In the process of electrodepositing indium, the step which comprises preparing a cyanide indium plating bath and adding leevulose thereto.

3. In the process of electrodepositing indium, the step which comprises preparing a cyanide indium plating bath and adding saccharose thereto.

l. In the process of electrodepositing indium, the step which comprises preparing a cyanide indium plating bath and adding thereto a saccharide of an order lower than a trisaccharide.

5. In the process of electrodepositing indium, the stepwhich comprises preparing a cyanide in dium plating bath and adding thereto a mono saccharide.

6. In the process; of electrodepositing indium, the step which comprises preparing a cyanide indium plating bath and adding thereto a disaccharide.

7. A cyanide electrolytic bath containing in-:' dium and containing a stabilizer such as a saccharide of a lower order thana trisaccharide.

8. A cyanide electrolytic bath containing. indium and containing a stabilizer such as a disaccharide. I

9. A cyanide electrolytic bath containing in diumv and'containing a stabilizer such as a mono= saccharide.

10. A cyanide electrolytic bath containing in= dium and containing a stabilizer such as dextrose.

11. A cyanide electrolytic bath containing in= dium and containing a stabilizer such as lavulose.

12. A cyanide electrolytic bath containing indium and containing a stabilizer such as sac= charose.

1 WILLIAM S. MURRAY.

DANIEL GRAY. 

